Internet Protocol (IP), such as IP over Ethernet, based packet transport over wavelength division multiplexing (WDM) systems has become the standard, and widely deployed, network architecture. Accordingly, this architecture includes at least an IP layer and a WDM layer and is typically referred to as a packet-optical transport architecture. Further, this architecture may include additional intermediate layers, such as a multi-protocol label switching (MPLS) layer and an Optical Transport Network (OTN) layer between the higher IP layer and the lower WDM layer.
In currently operating packet-optical networks, protection is performed predominantly at a packet layer, which may be the IP layer or, typically, a combination of the IP layer and the MPLS layer. Such layers can be acceptable for the requirements of packet-optical network protection mechanisms, which typically require responses of no more than a few tens of milliseconds.